The degree at which a nozzle needs to be cleaned is dependent upon the clearance around the nozzle body and the cavity insert along with the sealing/stacking surfaces of the components.

The entire nozzle does not need to be spotless with all traces of plastic removed to be reinstalled and seated properly. This can be accomplished a number of ways, depending upon the type of nozzle and how it is heated.

All that is necessary is to:

  Clean the nozzle housing front and back, and to remove enough plastic around the nozzle body so they can easily enter the back of the cavity without interference.
Plastic around the front tip must obviously be removed if it stacks and seals against the back of the cavity gate insert.

 Clean the back of the nozzle seats and run them over a medium Norton stone to make sure they are flat and smooth. If a depression is noted then this must be measured to ensure the depth of the depression is no greater than .001 or a slow leak could occur here (see Photos).

 Cartridge Heated Nozzles
If the nozzle has an internal cartridge heater that isn’t stuck, simply pull it out (make sure it is numbered) and use a soft wire wheel to clean off whatever plastic is on the body, taking care not to damage or reconfigure the tip.

  Some technicians like to burn the excess plastic off nozzle bodies with a torch, before disassembly and while the manifold plate is standing up on the bench. If this is your preference it is advised to use a controller (versus a torch) to heat up the nozzles just enough (usually around 250 to 300 degrees) to easily remove the plastic, which makes this operation safer and without stinking up the shop.

 If the heater cartridge is stuck, then you can either drill it out (thus scraping the heater) or leave it alone and clean off the nozzle body with a brass pick/scraper. You also can clamp it up in a vise (soft jaws) and use a wire  wheel in an air drill.

 Standard cartridge heaters are typically .005 smaller than the nozzle bore, but if not cleaned out periodically will stick hard. If you do have to drill it out, use the next standard size smaller bit, taking care not to scar up the bore walls. Resist the temptation to perform this operation by eye at the bench with a hand drill, instead use a lathe to do it right.

  The objective is to drill out all but the outer skin of the heater allowing you to slip a prick punch behind the skin, bend it in far enough to grasp it with needle nose pliers, hose it down with WD-40 and work it out. A time-consuming task that is best prevented through regular cleanings and the application of an anti-seize product like a release and transfer fluid before installing heaters.

  Cast-In Heated Nozzles
These are more of a pain to clean because of the attached heater/thermocouple wires that should not be removed for normal maintenance. They also require great care not to poke holes in the embedded heaters or to damage the leads and (ceramic) connectors. Never use a torch on these types of nozzles and only clean what is absolutely necessary to reinstall the nozzles.

 Banded Heater Nozzles
These are great simply because the heaters and thermocouple wires are usually easily removed, making cleaning the body much easier via ultrasonics.    Any time a component can be cleaned in an ultrasonic tank, the process will be faster. The only problem usually stems from removing the thermocouple.

  Some brands require you to straighten out the tip before you can slip it through the nozzle, which can stress crack and ruin the thermocouple. If this is the case, and the manifold is extremely time-consuming to work on, then spend the money and replace all of the thermocouples so as not to risk creating an opportunity for them to fail—negating all of your labor hours.

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